Transmitting pilot signals from a UE to multiple base stations

ABSTRACT

Methods, systems, and devices are described for wireless communication. In one method, a method of wireless communication at a user equipment (UE) includes receiving a synchronization signal. The synchronization signal may be common to a plurality of cells within a network. The method further includes acquiring a timing of the network based on the synchronization signal, and transmitting a pilot signal in response to acquiring the timing of the network. The pilot signal may identify the UE and be concurrently receivable by the plurality of cells within the network. Other aspects, features, and embodiments are also claimed and described.

CROSS REFERENCES

The present Application for Patent is a Divisional of U.S. patentapplication Ser. No. 14/728,756 by Ji et al., entitled “WirelessCommunication Systems and Methods Having a User Equipment-Centric MediumAccess Control Layer,” filed Jun. 2, 2015, and claims priority to U.S.Provisional Patent Application No. 62/074,488 by Ji et al., entitled“Wireless Communication System Having a User Equipment-Centric MediumAccess Control Layer,” filed Nov. 3, 2014, and U.S. Provisional PatentApplication No. 62/083,071 by Ji et al, entitled “Wireless CommunicationSystem Having a User Equipment-Centric Medium Access Control Layer,”filed Nov. 21, 2014, assigned to the assignee hereof, and expresslyincorporated by reference herein.

TECHNICAL FIELD

The present disclosure, for example, relates to wireless communicationsystems, and more particularly to a wireless communication system havinga user equipment (UE)-centric medium access control (MAC) layer.

INTRODUCTION

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, andorthogonal frequency-division multiple access (OFDMA) systems.

By way of example, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipments (UEs). A base station may communicate with UEs ondownlink channels (e.g., for transmissions from a base station to a UE)and uplink channels (e.g., for transmissions from a UE to a basestation).

In a wireless multiple-access communication system, each cell of anetwork may broadcast synchronization signals and system information forUEs to discover. Upon discovering the synchronization signals and systeminformation broadcast by a particular cell, a UE may perform an initialaccess procedure to access the network via the cell. The cell via whichthe UE accesses the network may become the UE's serving cell. As the UEmoves within the network, the UE may discover other cells (e.g.,neighboring cells) and determine whether a handover of the UE to aneighboring cell is warranted.

BRIEF SUMMARY

The present disclosure generally relates to wireless communicationsystems, and more particularly to a wireless communication system havinga UE-centric MAC layer. Wireless communication systems such as a LongTerm Evolution (LTE) communication systems or LTE-Advanced (LTE-A)communication systems have a network-centric MAC layer. In a wirelesscommunication system having a network-centric MAC layer, the networkperpetually broadcasts synchronization signals and system informationfor UEs to discover. Upon discovering the synchronization signals andsystem information broadcast by a particular cell, a UE may perform aninitial access procedure to access the network via the cell. Onceconnected to the network, the UE may discover other cells as it moveswithin the network. The other cells may broadcast differentsynchronization signals or system information.

A wireless communication system having a network-centric MAC layer mayentail various signal broadcasts. These broadcasts consume power and mayor may not be received or used by some or all of a cell's UEs. Awireless communication system having a network-centric MAC layer alsoplaces relatively more of the network processing on UEs (e.g., a UEidentifies a first serving cell upon initially accessing the network,and then identifies and monitors handover targets (other serving cells)as part of its mobility management).

The present disclosure describes a wireless communication system havinga UE-centric MAC layer. A wireless communication system having aUE-centric MAC layer may enable both UEs and base stations to conservepower among additional aspects and features as discussed in detailbelow. As further discussed below, UE-centric MAC features can enableand provide an edgeless network arrangement that can be useful ininternet of everything (IOE) applications where data rates will be high.

In a first set of illustrative examples, a method of wirelesscommunication at a UE is described. In one configuration, the method mayinclude receiving a synchronization signal. The synchronization signalmay be common to a plurality of cells within a network, and may bebroadcast from the plurality of cells in a single frequency network(SFN) manner. The method may also include acquiring a timing of thenetwork based on the synchronization signal, and transmitting a pilotsignal in response to acquiring the timing of the network. The pilotsignal may be concurrently receivable by the plurality of cells withinthe network.

In some embodiments, methods can have additional aspects and/orfeatures. For example, a method may include receiving, in response totransmitting the pilot signal, at least one of: on-demand systeminformation for the UE, an uplink allocation for the UE, or a downlinkcontrol channel message. Method embodiments, may also includetransmitting a radio resource control (RRC) connection request to thenetwork in response to receiving at least one of: the on-demand systeminformation for the UE or the uplink allocation for the UE.

In some embodiments, the method may include entering an RRC connectedstate with the network subsequent to acquiring the timing of thenetwork. In some configurations, the RRC connected state may include afirst RRC connected state in a plurality of RRC connected states, theplurality of RRC connected states may include a second RRC connectedstate, and the method may include switching between at least the firstRRC connected state and the second RRC connected state based at least inpart on a determined traffic level. In some configurations, the firstRRC connected state may be associated with a first discontinuousreception (DRX) cycle, the second RRC connected state may be associatedwith a second DRX cycle, and the second DRX cycle may differ from thefirst DRX cycle. In some configurations, the method may includedetermining the traffic level based on at least one of: anetwork-transmitted traffic level indicator; a network command; a statusof a timer maintained at the UE; or a buffer status of the UE.

In some embodiments, the method may include, when operating in the firstRRC connected state: transmitting, according to a first DRX cycle, atleast one of: a scheduling request (SR), a buffer status report (BSR), aconnected state pilot signal, or an indicator of a channel quality basedon a reference signal configured for and received by the UE; andmonitoring a grant channel for an identifier of the UE. In someconfigurations, the method may include receiving over the grant channel,in response to the monitoring, a paging signal or uplink grantassociated with the identifier of the UE. In some configurations, themethod may include, when operating in the first RRC connected state,measuring a reference signal, and determining to perform a constellationreselection based at least in part on the measuring. In someconfigurations, the reference signal may include a beamformed channelstate information reference signal (CSI-RS) received from the network.

In some embodiments, the method may include, when operating in thesecond RRC connected state: transmitting a connected state pilot signalaccording to a second DRX cycle; and monitoring a grant channel for anidentifier of the UE. In some configurations, the method may alsoinclude, when operating in the second RRC connected state: periodicallylistening for a keep alive signal from the network; and determining toperform a constellation reselection based at least in part on ameasurement of the keep alive signal or a decoding error of the keepalive signal.

In some embodiments, the method may include receiving from the network areselection command; selecting, in response to the reselection command,a new constellation; and transmitting the pilot signal in response to asecond synchronization signal received from the new constellation.

In some embodiments of them method, the synchronization signal mayinclude system information request configuration information includingat least one of: an indication of a SIB request bandwidth, an indicationof a SIB request timing, a portion of a constellation identifier, ornetwork access barring information. In some embodiments of the method,the pilot signal may include a spatial signature. In some embodiments ofthe method, the pilot signal may include a sounding reference signal(SRS).

In a second set of illustrative examples, a device for wirelesscommunication at a UE is described. In one configuration, the device mayinclude means for receiving a synchronization signal, means foracquiring a timing of the network based on the synchronization signal,and means for transmitting a pilot signal in response to acquiring thetiming of the network. The synchronization signal may be common to aplurality of cells within the network, and may be received as a SFNbroadcast. The pilot signal may be concurrently receivable by theplurality of cells within the network. In some examples, the apparatusmay further include means for implementing one or more aspects of themethod for wireless communication described above with respect to thefirst set of illustrative examples.

In a third set of illustrative examples, another device for wirelesscommunication at a UE is described. In one configuration, the device mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to receive a synchronization signal,acquire a timing of the network based on the synchronization signal, andtransmit a pilot signal in response to acquiring the timing of thenetwork. The synchronization signal may be common to a plurality ofcells within a network, and may be received as a SFN broadcast. Thepilot signal may be concurrently receivable by the plurality of cellswithin the network. In some examples, the instructions may also beexecutable by the processor to implement one or more aspects of themethod for wireless communication described above with respect to thefirst set of illustrative examples.

In a fourth set of illustrative examples, a non-transitorycomputer-readable medium storing computer-executable code for wirelesscommunication at a UE is described. The code may be executable by aprocessor to receive a synchronization signal, acquire a timing of thenetwork based on the synchronization signal, and transmit a pilot signalin response to acquiring the timing of the network. The synchronizationsignal may be common to a plurality of cells within a network, and maybe received as a SFN broadcast. The pilot signal may be concurrentlyreceivable by the plurality of cells within the network. In someexamples, the code may also be used to implement one or more aspects ofthe method for wireless communication described above with respect tothe first set of illustrative examples.

In a fifth set of illustrative examples, a method of wirelesscommunication at a base station is described. The method may includebroadcasting a synchronization signal. The synchronization signal may becommon to a plurality of cells within a network, and may be received asa SFN broadcast. The method may also include receiving a number of pilotsignals from a first number of UEs. Each of the number of pilot signalsmay identify a UE in the first number of UEs and be concurrentlyreceivable by the plurality of cells within the network.

In some embodiments, the method may include identifying, from the firstnumber of UEs, a second number of UEs for which the base station willserve as a serving cell. In some configurations, the method may includetransmitting information corresponding to the number of pilot signals toa central node, and receiving an indication of the second number of UEsfrom the central node.

In a sixth set of illustrative examples, a device for wirelesscommunication at a base station is described. In one configuration, thedevice may include means for broadcasting a synchronization signal. Thesynchronization signal may be common to a plurality of cells within anetwork, and may be received as a SFN broadcast. The device may alsoinclude means for receiving a number of pilot signals from a firstnumber of UEs. Each of the number of pilot signals may identify a UE inthe first number of UEs and be concurrently receivable by the pluralityof cells within the network. In some examples, the apparatus may furtherinclude means for implementing one or more aspects of the method forwireless communication described above with respect to the fifth set ofillustrative examples.

In a seventh set of illustrative examples, another device for wirelesscommunication at a base station is described. In one configuration, thedevice may include a processor, memory in electronic communication withthe processor, and instructions stored in the memory. The instructionsmay be executable by the processor to broadcast a synchronizationsignal. The synchronization signal may be common to a plurality of cellswithin a network, and may be received as a SFN broadcast. Theinstructions may also be executable by the processor to receive a numberof pilot signals from a first number of UEs. Each of the number of pilotsignals may identify a UE in the first number of UEs and be concurrentlyreceivable by the plurality of cells within the network. In someexamples, the instructions may also be executable by the processor toimplement one or more aspects of the method for wireless communicationdescribed above with respect to the fifth set of illustrative examples.

In an eighth set of illustrative examples, a non-transitorycomputer-readable medium storing computer-executable code for wirelesscommunication at a base station is described. In one configuration, thecode may be executable by a processor to broadcast a synchronizationsignal. The synchronization signal may be common to a plurality of cellswithin a network, and may be received as a SFN broadcast. The code mayalso be executable by the processor to receive a number of pilot signalsfrom a first number of UEs. Each of the number of pilot signals mayidentify a UE in the first number of UEs and be concurrently receivableby the plurality of cells within the network. In some examples, the codemay also be used to implement one or more aspects of the method forwireless communication described above with respect to the fifth set ofillustrative examples

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages are below. The conception and specific examplesdisclosed may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes of the presentdisclosure. Such equivalent constructions do not depart from the scopeof the appended claims. Characteristics of the concepts disclosedherein, both their organization and method of operation, together withassociated advantages will be better understood from the followingdescription when considered in connection with the accompanying figures.Each of the figures is provided for the purpose of illustration anddescription only, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 illustrates an example of a wireless communication system inaccordance with various aspects of the present disclosure;

FIG. 2 shows an exemplary timeline of a UE-centric initial access to anetwork, in accordance with various aspects of the present disclosure;

FIG. 3 shows an exemplary RRC state diagram for a UE, in accordance withvarious aspects of the present disclosure;

FIG. 4 shows an exemplary timeline for network-managed mobility,frequency reselection, and constellation reselection, in accordance withvarious aspects of the present disclosure;

FIG. 5 shows an exemplary timeline for UE-managed frequency reselectionor constellation reselection in the event of radio link failure, inaccordance with various aspects of the present disclosure;

FIG. 6 shows a block diagram of a UE for use in wireless communication,in accordance with various aspects of the present disclosure;

FIG. 7 shows a block diagram of a UE for use in wireless communication,in accordance with various aspects of the present disclosure;

FIG. 8 shows a block diagram of a base station for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 9 shows a block diagram of a base station for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 10 shows a block diagram of a central node for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 11 shows a block diagram of a central node for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 12 shows a block diagram of a UE for use in wireless communication,in accordance with various aspects of the present disclosure;

FIG. 13 shows a block diagram of a base station (e.g., a base stationforming part or all of an eNB) for use in wireless communication, inaccordance with various aspects of the present disclosure;

FIG. 14 shows a block diagram of a central node, in accordance withvarious aspects of the present disclosure;

FIG. 15 is a block diagram of a MIMO communication system including abase station and a UE, in accordance with various aspects of the presentdisclosure;

FIG. 16 is a flow chart illustrating an example of a method for wirelesscommunication at a UE, in accordance with various aspects of the presentdisclosure;

FIG. 17 is a flow chart illustrating an example of a method for wirelesscommunication at a UE, in accordance with various aspects of the presentdisclosure;

FIG. 18 is a flow chart illustrating an example of a method for wirelesscommunication at a UE, in accordance with various aspects of the presentdisclosure;

FIG. 19 is a flow chart illustrating an example of a method for wirelesscommunication at a base station, in accordance with various aspects ofthe present disclosure;

FIG. 20 is a flow chart illustrating an example of a method for wirelesscommunication at a base station, in accordance with various aspects ofthe present disclosure;

FIG. 21 is a flow chart illustrating an example of a method for managingwireless communication at a central node, in accordance with variousaspects of the present disclosure; and

FIG. 22 is a flow chart illustrating an example of a method for managingwireless communication at a central node, in accordance with variousaspects of the present disclosure.

DETAILED DESCRIPTION

The described features generally relate to a wireless communicationsystem having a UE-centric MAC layer. A wireless communication systemhaving a UE-centric MAC layer may be advantageous, in some respects, ina time-domain duplex (TDD) system having a large antenna array. Thelarge antenna array may have limited coverage for broadcast channels(e.g., the channels that broadcast synchronization signals and systeminformation in a wireless communication system having a network-centricMAC layer). As described in the present disclosure, a wirelesscommunication system having a network-centric MAC layer may forego thebroadcast of system information, as well as some cell-specificsynchronization signals. A wireless communication system having aUE-centric MAC layer may also be advantageous, in some respects, in thatmobility measurements can contribute to UE power consumption, and awireless communication system having a UE-centric MAC layer can offloadmany mobility measurements previously performed by UEs to the network. Awireless communication system having a UE-centric MAC layer may alsooffload handover and cell reselection processing and decisions to thenetwork side, which, when performed by a UE in a network-centricwireless communication system can be a major source of jitter and calldrops. A wireless communication system having a UE-centric MAC layer mayalso be advantageous, in some respects, because the broadcast of systeminformation and cell-specific information by a base station cancontribute significantly to the power consumption of the base station.As previously indicated, a base station in a wireless communicationsystem having a UE-centric MAC layer may often forego the broadcast ofsystem information or cell-specific information.

Techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (WI-FI), IEEE 802.16 (WIMAX), IEEE 802.20, Flash-OFDM™, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTEAdvanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies, including cellular (e.g., LTE) communicationsover a shared radio frequency spectrum band. The description below,however, describes an LTE/LTE-A system for purposes of example, and LTEterminology is used in much of the description below, although thetechniques are applicable beyond LTE/LTE-A applications (e.g., to 5Gnetworks or other next generation communication systems).

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in other examples.

FIG. 1 illustrates an example of a wireless communication system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunication system 100 may include one or more base stations 105, oneor more UEs 115, and a core network 130. The core network 130 mayprovide user authentication, access authorization, tracking, internetprotocol (IP) connectivity, and other access, routing, or mobilityfunctions. The base stations 105 may interface with the core network 130through backhaul links 132 (e.g., S1, etc.). The base stations 105 mayperform radio configuration and scheduling for communication with theUEs 115, or may operate under the control of a base station controller(not shown). In various examples, the base stations 105 may communicate,either directly or indirectly (e.g., through core network 130), with oneanother over backhaul links 134 (e.g., X1, etc.), which may be wired orwireless communication links.

The base stations 105 may wirelessly communicate with the UEs 115 viaone or more base station antennas. Each of the base stations 105 mayprovide communication coverage for a respective geographic coverage area110. In some examples, base stations 105 may be referred to as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, eNodeB (eNB), Home NodeB, a Home eNodeB, or someother suitable terminology. The geographic coverage area 110 for a basestation 105 may be divided into sectors making up only a portion of thecoverage area (not shown). The wireless communication system 100 mayinclude base stations 105 of different types (e.g., macro or small cellbase stations). There may be overlapping geographic coverage areas 110for different technologies.

In some examples, the wireless communication system 100 may be orinclude a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) network. Thewireless communication system 100 may also be a next generation network,such as a 5G wireless communication network. In LTE/LTE-A networks, theterm evolved node B (eNB) may be generally used to describe the basestations 105, while the term UE may be generally used to describe theUEs 115. The wireless communication system 100 may be a heterogeneousLTE/LTE-A network in which different types of eNBs provide coverage forvarious geographical regions. For example, each eNB or base station 105may provide communication coverage for a macro cell, a small cell, orother types of cell. The term “cell” is a 3GPP term that can be used todescribe a base station, a carrier or component carrier associated witha base station, or a coverage area (e.g., sector, etc.) of a carrier orbase station, depending on context.

A macro cell may generally cover a relatively large geographic area(e.g., several kilometers in radius) and may allow unrestricted accessby UEs 115 with service subscriptions with the network provider.

A small cell may include a lower-powered base station, as compared witha macro cell, that may operate in the same or different (e.g., licensed,unlicensed, etc.) frequency bands as macro cells. Small cells mayinclude pico cells, femto cells, and micro cells according to variousexamples. A pico cell, for example, may cover a small geographic areaand may allow unrestricted access by UEs 115 with service subscriptionswith the network provider. A femto cell may also cover a smallgeographic area (e.g., a home) and may provide restricted access by UEs115 having an association with the femto cell (e.g., UEs 115 in a closedsubscriber group (CSG), UEs 115 for users in the home, and the like). AneNB for a macro cell may be referred to as a macro eNB. An eNB for asmall cell may be referred to as a small cell eNB, a pico eNB, a femtoeNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells (e.g., component carriers).

The communication networks that may accommodate some of the variousdisclosed examples may be packet-based networks that operate accordingto a layered protocol stack and data in the user plane may be based onthe IP. A radio link control (RLC) layer may perform packet segmentationand reassembly to communicate over logical channels. A MAC layer mayperform priority handling and multiplexing of logical channels intotransport channels. The MAC layer may also use HARQ to provideretransmission at the MAC layer to improve link efficiency. In thecontrol plane, the radio resource control (RRC) protocol layer mayprovide establishment, configuration, and maintenance of an RRCconnection between a UE 115 and the base stations 105. The RRC protocollayer may also be used for core network 130 support of radio bearers forthe user plane data. At the physical (PHY) layer, the transport channelsmay be mapped to physical channels.

The UEs 115 may be dispersed throughout the wireless communicationsystem 100, and each UE 115 may be stationary or mobile. A UE 115 mayalso include or be referred to by those skilled in the art as a mobilestation, a subscriber station, a mobile unit, a subscriber unit, awireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a user agent, a mobile client, a client, orsome other suitable terminology. A UE 115 may be a cellular phone, apersonal digital assistant (PDA), a wireless modem, a wirelesscommunication device, a handheld device, a tablet computer, a laptopcomputer, a cordless phone, a wireless local loop (WLL) station, anentertainment device, a vehicular component, or the like. A UE may beable to communicate with various types of base stations and networkequipment including macro eNBs, small cell eNBs, relay base stations,and the like.

The wireless communication links 125 shown in wireless communicationsystem 100 may carry UL transmissions from a UE 115 to a base station105, or downlink (DL) transmissions, from a base station 105 to a UE115. The downlink transmissions may also be called forward linktransmissions while the uplink transmissions may also be called reverselink transmissions. Each wireless communication link 125 may include oneor more carriers, where each carrier may be a signal made up of multiplesub-carriers (e.g., waveform signals of different frequencies) modulatedaccording to the various radio technologies described above. Eachmodulated signal may be sent on a different sub-carrier and may carrycontrol information (e.g., reference signals, control channels, etc.),overhead information, user data, etc. The communication links 125 maytransmit bidirectional communications using frequency division duplex(FDD) (e.g., using paired spectrum resources) or time division duplex(TDD) operation (e.g., using unpaired spectrum resources). Framestructures may be defined for FDD (e.g., frame structure type 1) and TDD(e.g., frame structure type 2).

In some embodiments of the wireless communication system 100, basestations 105 or UEs 115 may include multiple antennas for employingantenna diversity schemes to improve communication quality andreliability between base stations 105 and UEs 115. Additionally oralternatively, base stations 105 or UEs 115 may employ multiple inputmultiple output (MIMO) techniques that may take advantage of multi-pathenvironments to transmit multiple spatial layers carrying the same ordifferent coded data.

Wireless communication system 100 may support operation on multiplecells or carriers, a feature which may be referred to as carrieraggregation (CA) or multi-carrier operation. A carrier may also bereferred to as a component carrier (CC), a layer, a channel, etc. Theterms “carrier,” “component carrier,” “cell,” and “channel” may be usedinterchangeably herein. A UE 115 may be configured with multipledownlink CCs and one or more uplink CCs for carrier aggregation. Carrieraggregation may be used with both FDD and TDD component carriers.

In some embodiments of the wireless communication system 100, thewireless communication system 100 may have a UE-centric MAC layer. Onthe network side, the base stations 105 may broadcast a synchronizationsignal. The UEs 115 may receive the synchronization signal, acquire atiming of the network from the synchronization signal, and in responseto acquiring the timing of the network, transmit a pilot signal. Thepilot signal transmitted by a UE 115 may be concurrently receivable by aplurality of cells (e.g., base stations) within the network. Each of theplurality of cells may measure a strength of the pilot signal, and thenetwork (e.g., one or more of the base stations 105 and/or a centralnode within the core network 130) may determine a serving cell for theUE 115. As the UE 115 continues to transmit a pilot signal, the networkmay handover the UE 115 from one serving cell to another, with orwithout informing the UE 115. System information may be transmitted toUEs 115 on-demand (e.g., in response to a UE 115 transmits a pilotsignal), thereby enabling the network to forego broadcasting the systeminformation and enabling the network to conserve power.

FIG. 2 shows an exemplary timeline 200 of a UE-centric initial access toa network, in accordance with various aspects of the present disclosure.The initial access procedure may be performed by a UE in communicationwith a base station. In some examples, the UE may be one of the UEs 115described with reference to FIG. 1, and the base station may be one ofthe base stations 105 described with reference to FIG. 1.

As shown in FIG. 2, a base station may broadcast a synchronizationsignal 205. The synchronization signal 205 may be common (e.g.,non-cell-specific) to a plurality of cells within a network, and may bereceived from at least one of the plurality of cells (e.g., from atleast one of a plurality of base stations in the cells) as a SFNbroadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal 205 may be aperiodic signal. In some embodiments, the synchronization signal 205 mayhave a relatively short duration or be transmitted relativelyinfrequently. For example, the synchronization signal 205 may have aduration of one symbol and be transmitted once every ten seconds. Inother examples, the synchronization signal 205 may be transmitted morefrequently, such as once per radio frame. In some embodiments, thesynchronization signal 205 may carry a few bits of information, such as4-6 bits of information. In some embodiments, the synchronization signal205 may include system information request configuration information(e.g., system information block (SIB) request). The system informationrequest configuration information may, in some examples, include atleast one of an indication of a SIB request bandwidth, an indication ofa SIB request timing (e.g., slot/symbol timing), a portion of aconstellation identifier, or network access barring information (e.g.,an indication of times when UEs of particular types may not transmit aSIB request). In some embodiments, the synchronization signal 205 may bemore dynamic and be broadcast on a synchronization channel with guard.

A UE may receive the synchronization signal 205 and acquire a timing ofthe network based on the synchronization signal 205. In response toacquiring the timing of the network, the UE may transmit a pilot signal210. The pilot signal 210 may be concurrently receivable by theplurality of cells within the network. In some embodiments, the pilotsignal 210 may include a spatial signature (e.g., an SRS). The basestation may in some cases have a large uplink spatial multiplexingcapacity for receiving the SRS. In some embodiments, the pilot signal210 may be transmitted in a SIB request occasion indicated by systeminformation request configuration information received with thesynchronization signal.

Following transmission of an instance of the pilot signal 210, the UEmay listen for a transmission from the network (e.g., a transmission,from the base station, of on-demand system information for the UE or anuplink allocation for the UE). In some embodiments, the UE may listenfor transmissions during a listening window 215. When the UE does notreceive a transmission during the listening window 215, the UE maytransition a receiver of the UE to a low power or OFF state until a nextlistening window 215, which may conserve power.

The base station may receive the pilot signal 210 and measure the pilotsignal 210 for purposes of initial access to the network. Other basestations (or cells) may also receive and measure the pilot signal 210. Aserving cell for the UE may be selected by one of the base stations, orby a central node in communication with the base stations, based atleast in part on the measurements of the pilot signal 210. For example,each of a number of base stations may measure the power (P_(PS)) of thepilot signal (PS) 210, and a serving cell for the UE may be selectedbased on a function such as:

${{serving}\mspace{14mu}{cell}} = {\underset{i}{\arg\;\max}\; P_{{PS}_{i}}}$where P_(PS) _(i) is the measured power of a serving cell i, and wherethe serving cell selected for the UE is the serving cell that receivesthe pilot signal 210 at a greatest power. Serving cell selection istherefore handled (at least primarily) by the network, and the number ofmeasurements performed by the UE, or processes managed by the UE, may bereduced.

When the base station has information to transmit to the UE, indicatedby data arrival 220, the base station may transmit a unicast pagingsignal 225 to the UE. In some embodiments, the unicast paging signal 225may be transmitted with on-demand system information for the UE (e.g.,an on-demand SIB or MIB). In some examples, the base station mayinitiate communication with a plurality of UEs using a multicast pagingsignal. Following receipt of a paging signal (e.g., the unicast pagingsignal 225), the UE may increase the duration of its current listeningwindow 215, and in some cases transmit a radio resource control (RRC)connection request 230 to the base station (e.g., an LTE/LTE-A randomaccess channel (RACH) message 3 (MSG3)). In some cases, the base stationmay transmit additional connection setup information 235 to the UE, orperform additional contention resolution procedures, following receiptof the RRC connection request 230.

When the UE has information to transmit to the base station, the UE maytransmit a scheduling request (SR) with one or more instances of thepilot signal 210. In response to receiving the pilot signal 210 or thescheduling request, the base station may transmit on-demand systeminformation (e.g., an on-demand system information block (SIB) or masterinformation block (MIB)) to the UE. The base station may also transmitan uplink allocation (e.g., an uplink grant) to the UE. In someembodiments, the system information and uplink allocation may betransmitted to the UE in a same downlink transmission. In some cases,the uplink allocation may be spatially multiplexed. Following receipt ofan uplink allocation, the UE may increase the duration of its currentlistening window 215, and in some cases may transmit an RRC connectionrequest 230 to the base station (e.g., an LTE/LTE-A RACH MSG3). In somecases, the base station may transmit additional connection setupinformation 235 to the UE, or perform additional contention resolutionprocedures, following receipt of the RRC connection request 230.

When system information is transmitted from the base station to a numberof UEs on-demand (e.g., when needed for an uplink or downlinktransmission between the base station and one or more of the UEs), thebase station may reduce or eliminate periodic broadcasts of systeminformation, which may conserve power. On the UE side, a UE may conservepower by not listening for system information broadcasts, and insteadonly listening for on-demand system information transmissions.

In some embodiments of the timeline 200 shown in FIG. 2, differentsynchronization signals may be transmitted for different constellations(e.g., different groups of cells, nodes, or base stations of thenetwork, or different groups of cells, nodes, or base stations belongingto different networks).

FIG. 3 shows an exemplary RRC state diagram 300 for a UE, in accordancewith various aspects of the present disclosure. In some examples, the UEmay be one of the UEs 115 described with reference to FIG. 1.

As shown in FIG. 3, State 1 may be a state in which a UE is detachedfrom a network. When in State 1, the UE may perform a procedure toaccess the network (e.g., an initial access or reconnection procedure).Upon accessing the network (indicated by transition 305), the UE mayenter State 2. Upon entering State 2, the network may allocate an“active set”/“paging area” to monitor mobility of the UE. The networkmay also monitor traffic of the UE. Upon the UE entering State 2, thenetwork may maintain an activate context for the UE until the UE leavesthe network.

State 2 may be an RRC connected sate. Upon entering State 2, the UE mayremain in an RRC connected state (e.g., not enter an idle state) untilleaving the network. As shown, State 2 may be an RRC_SHORT state. TheRRC_SHORT state may be associated with a first DRX cycle (e.g., a shortDRX cycle). When operating in the RRC_SHORT state, the network mayallocate a downlink (DL) channel state information reference signal(CSI-RS), such as a beamformed CSI-RS for channel quality indication(CQI) reporting. The network may also allocate uplink (UL) resources forcontrol channels. Also when operating in the RRC_SHORT state, the UE maytransmit, according to the first DRX cycle, at least one of: an SR, abuffer status report (BSR), a connected state pilot signal (e.g., anSRS), or an indicator of a channel quality based on a reference signal(e.g., a beamformed CSI-RS) configured for and received by the UE. Theconnected state pilot signal may be transmitted using resources (e.g.,time and frequency resources) identified by the network for the UE, andmay include an identifier of the UE. The UE may also monitor a grantchannel (e.g., a physical downlink control channel (PDCCH)) for anidentifier of the UE (e.g., a cell radio network temporary identifier(C-RNTI)). The grant channel may carry, for example, paging signals oruplink grants for the UE.

When operating in the RRC_SHORT state, the UE may determine a trafficlevel (a level of uplink and/or downlink traffic between the UE and thenetwork). In some embodiments, the traffic level may be determined basedon at least one of: a network-transmitted traffic level indicator; anetwork command; a status of a timer maintained at the UE; or a bufferstatus of the UE. When it is determined that the traffic level satisfiesa threshold (e.g., when the traffic level is high enough), the UE mayremain in the RRC_SHORT state, as indicated by transition 310. When itis determined that the traffic level does not satisfy a threshold, theUE may transition to State 3 (indicated by 315).

State 3 may be another RRC connected sate. As shown, State 3 may be anRRC_LONG state. The RRC_LONG state may be associated with a second DRXcycle (e.g., a long DRX cycle, which may be longer than the short DRXcycle of the RRC_SHORT state). When operating in the RRC_LONG state, thenetwork may allocate uplink (UL) resources for the transmission of aconnected state pilot signal (e.g., an SRS). Also when operating in theRRC_LONG state, the UE may transmit the pilot signal according to thesecond DRX cycle. The UE may also monitor a grant channel (e.g., thePDCCH) for an identifier of the UE (e.g., a C-RNTI). The RRC_LONG statemay enable the UE to conserve power by enabling the UE to sleep betweenperiodic wake ups (indicated by 320) for monitoring and signaltransmission.

In some embodiments, the traffic level may be compared to a firstthreshold when determining whether to switch from the RRC_SHORT state tothe RRC_LONG state (indicated by 315), and the traffic level may becompared to a second threshold when determining whether to switch fromthe RRC_LONG state to the RRC_SHORT state (indicated by 325).

FIG. 4 shows an exemplary timeline 400 for network-managed mobility andconstellation reselection, in accordance with various aspects of thepresent disclosure. The timeline 400 shows communications between a UEand a base station. In some examples, the UE may be one of the UEs 115described with reference to FIG. 1, and the base station may be one ofthe base stations 105 described with reference to FIG. 1.

As shown in FIG. 4, a base station may broadcast a synchronizationsignal 405. A UE may receive the synchronization signal 405, acquire atiming of the network based on the synchronization signal 405, and inresponse to acquiring the timing of the network, transmit a pilot signal410. The pilot signal 410 may identify the UE and be concurrentlyreceivable by the plurality of cells within the network. In someembodiments, the pilot signal 410 may include a spatial signature (e.g.,an SRS). Following transmission of an instance of the pilot signal 410,the UE may listen for a transmission from the network (e.g., atransmission of a paging signal or uplink allocation from the basestation, which transmission may include on-demand system information)during a listening window 415. When the UE does not receive atransmission during the listening window 415, the UE may transition areceiver to a low power or OFF state until a next listening window 415,which may conserve power. Further exemplary details concerning thesynchronization signal 405, the pilot signal 410, or the listeningwindow 415 are described with reference to FIG. 2 and thesynchronization signal 205, the pilot signal 210, or the listeningwindow 215.

The base station may also measure the pilot signal 410 for purposes ofinitial access to the network, or for mobility management orconstellation reselection within the network. Other base stations (orcells) may also receive and measure the pilot signal 410 and obtain theidentity of the UE. In some cases, each of a number of base stations maymeasure the power (P_(PS)) of the pilot signal (PS) 410 at a measurementtime 420, and a serving cell (e.g., a handover target) for the UE may beselected based on a function such as:

${{serving}\mspace{14mu}{cell}} = {\underset{i}{\arg\;\max}\; P_{{PS}_{i}}}$where P_(PS) _(i) is the measured power of a serving cell i, and wherethe serving cell selected for the UE is the serving cell that receivesthe pilot signal 410 at a greatest power. A handover target may beselected after receipt of each instance of the pilot signal 410, or lessfrequently. A handover target may also be selected when a measurement425 of the power of the pilot signal 410 by the current serving cellfalls below a threshold (e.g., T_serving_low). A change in serving cellfor the UE may be transparent to the UE.

In some embodiments, the base station may receive measurements of thepower of the pilot signal 410 from other base stations and determinewhether it is the serving cell for the UE. In some embodiments, the basestation may transmit a measurement of the power of the pilot signal 410to a central node, and receive (or not receive) an indication that thebase station is a serving cell for the UE. Serving cell selection andmobility management is therefore handled (at least primarily) by thenetwork, and the number of measurements performed by the UE, orprocesses managed by the UE, may be reduced.

Under some scenarios, a base station or central node may not identify ahandover target for the UE, but may determine that a frequencyreselection or constellation reselection is warranted (e.g., because theUE is moving out of coverage). Under such scenarios, the base stationoperating as the current serving cell may transmit a reselection command430 to the UE, and the UE may perform a frequency reselection orconstellation reselection (e.g., as indicated by the reselection command430, or as determined by the UE). The UE may then report a result 435 ofits frequency reselection or constellation reselection to the basestation.

FIG. 5 shows an exemplary timeline 500 for UE-managed frequencyreselection or constellation reselection in the event of radio linkfailure, in accordance with various aspects of the present disclosure.The timeline 500 shows communications between a UE and a base station.In some examples, the UE may be one of the UEs 115 described withreference to FIG. 1, and the base station may be one of the basestations 105 described with reference to FIG. 1.

As shown in FIG. 5, a base station may broadcast a synchronizationsignal 505. A UE may receive the synchronization signal 505, acquire atiming of the network based on the synchronization signal 505, and inresponse to acquiring the timing of the network, transmit a pilot signal510. The pilot signal 510 may identify the UE and be concurrentlyreceivable by the plurality of cells within the network. In someembodiments, the pilot signal 510 may include a spatial signature (e.g.,an SRS). Following transmission of an instance of the pilot signal 510,the UE may listen for a transmission from the network (e.g., atransmission of a paging signal or uplink allocation from the basestation, which transmission may include on-demand system information)during a listening window 515. When the UE does not receive atransmission during the listening window 515, the UE may transition areceiver to a low power or OFF state until a next listening window 515,which may conserve power. Further exemplary details concerning thesynchronization signal 505, the pilot signal 510, or the listeningwindow 515 are described with reference to FIG. 2 and thesynchronization signal 205, the pilot signal 210, or the listeningwindow 215.

Under some scenarios, such as, when the UE is operating in the RRC_LONGstate described with reference to FIG. 3, the UE may measure a strengthof a signal 520 (e.g., a reference signal, such as a CSI-RS orbeamformed CSI-RS) received from the base station to predict controlerror. The UE may receive the signal 520 during one or more of thelistening windows 515. When the strength of the signal indicates a lowsignal-to-noise ratio (SNR), the UE may perform a constellationreselection based at least in part on the measurement of the signal 520,and upon successfully performing the constellation reselection, transmita pilot signal 525 to the new constellation.

Under other scenarios, such as, when the UE is operating in the RRC_LONGstate described with reference to FIG. 3, the UE may receive, or receiveand measure a strength of, a signal 520 (e.g., a keep alive signal)received from the base station. The UE may receive the signal 520 duringone or more of the listening windows 515. However, in the case of radiolink failure (RLF), the UE may not receive one or more instances of thesignal 520. Or, the UE may determine that the strength of the signalindicates a low SNR. In such cases, the UE may perform a constellationreselection based at least in part on the signal 520 (e.g., based atleast in part on non-receipt of or measurement of the signal 520). Uponsuccessfully performing the constellation reselection, the UE maytransmit a pilot signal 525 to the new constellation.

In some configurations, a keep alive signal may be transmitted onresources (e.g., time and frequency resources) allocated to a particularUE. In some configurations, a keep alive signal may carry power controlinformation or timing advance information. In some embodiments, a keepalive signal may be transmitted according to a duty cycle based on UEchannel condition. In some embodiments, a UE may be compute a referencesignal received power (RSRP) and determine whether to perform afrequency reselection or constellation reselection based at least inpart on the RSRP.

FIG. 6 shows a block diagram 600 of a UE 115-a for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. The UE 115-a may be an example of aspects of one or more ofthe UEs 115 described with reference to FIG. 1. The UE 115-a may also beor include a processor (e.g., an ASIC (as discussed below) or specialpurpose processor configured to control one or more functions of the UE115). The UE 115-a may include a receiver module 610, a wirelesscommunication management module 620, or a transmitter module 630. Eachof these modules may be in communication with each other.

The modules of the UE 115-a may, individually or collectively, beimplemented using one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other examples, other types of integrated circuits may be used (e.g.,Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), andother Semi-Custom ICs), which may be programmed in any manner known inthe art. The functions of each module may also be implemented, in wholeor in part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 610 may include at least one radiofrequency (RF) receiver. The receiver module 610 or RF receiver may beused to receive various types of data or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 described with reference to FIG. 1.

In some examples, the transmitter module 630 may include at least one RFtransmitter. The transmitter module 630 or RF transmitter may be used totransmit various types of data or control signals (i.e., transmissions)over one or more communication links of a wireless communication system,such as one or more communication links of the wireless communicationsystem 100 described with reference to FIG. 1.

The wireless communication management module 620 may be used to manageone or more aspects of wireless communication for the UE 115-a. In someexamples, the wireless communication management module 620 may include asynchronization signal processing module 635 or a pilot signaltransmission management module 645.

The synchronization signal processing module 635 may be used to receivea synchronization signal. The synchronization signal may be common(e.g., non-cell specific) to a plurality of cells within a network, andmay be received from at least one of the plurality of cells (e.g., fromat least one of a plurality of base stations in the cells) as a SFNbroadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal may be aperiodic signal. In some embodiments, the synchronization signal mayinclude system information request (e.g., SIB request) configurationinformation. The configuration information may, in some examples,include at least one of an indication of a SIB request bandwidth, anindication of a SIB request timing (e.g., slot/symbol timing), a portionof a constellation identifier, or network access barring information(e.g., an indication of times when UEs of particular types may nottransmit a SIB request).

The synchronization signal processing module 635 may include a networktiming acquisition module 640. The network timing acquisition module 640may be used to acquire a timing of the network based on thesynchronization signal.

The pilot signal transmission management module 645 may be used totransmit a pilot signal in response to acquiring the timing of thenetwork. The pilot signal may be concurrently receivable by theplurality of cells within the network. In some embodiments, the pilotsignal may include a spatial signature (e.g., an SRS). In someembodiments, the pilot signal may be transmitted in a SIB requestoccasion indicated by system information request configurationinformation received with the synchronization signal, and may betransmitted with a random sequence usable by a base station totemporarily identify the UE during initial acquisition.

FIG. 7 shows a block diagram 700 of a UE 115-b for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. The UE 115-b may be an example of aspects of one or more ofthe UEs 115 described with reference to FIG. 1 or 6. The UE 115-b mayalso be or include a processor. The UE 115-b may include a receivermodule 610, a wireless communication management module 620-a, or atransmitter module 630. Each of these modules may be in communicationwith each other.

The modules of the UE 115-b may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each module may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some embodiments, the receiver module 610 or transmitter module 630may be configured as described with reference to FIG. 6.

The wireless communication management module 620-a may be used to manageone or more aspects of wireless communication for the UE 115-b. In someexamples, the wireless communication management module 620-a may includea synchronization signal processing module 635-a, a pilot signaltransmission management module 645-a, a system information processingmodule 705, an uplink/downlink allocation processing module 710, an RRCconnection management module 715, a scheduling request management module720, a buffer status report management module 725, a CQI managementmodule 730, a grant management module 735, a measurement module 740, aconstellation reselection module 745, or a traffic level determinationmodule 750.

The synchronization signal processing module 635-a may be used toreceive a synchronization signal. The synchronization signal may becommon (e.g., non-cell specific) to a plurality of cells within anetwork, and may be received from at least one of the plurality of cells(e.g., from at least one of a plurality of base stations in the cells)as a SFN broadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal may be aperiodic signal. In some embodiments, the synchronization signal mayinclude system information request (e.g., SIB request) configurationinformation. The configuration information may, in some examples,include at least one of an indication of a SIB request bandwidth, anindication of a SIB request timing (e.g., slot/symbol timing), a portionof a constellation identifier, or network access barring information(e.g., an indication of times when UEs of particular types may nottransmit a SIB request).

The synchronization signal processing module 635-a may include a networktiming acquisition module (not shown), which may be used to acquire atiming of the network based on the synchronization signal.

The pilot signal transmission management module 645-a may be used totransmit a pilot signal in response to acquiring the timing of thenetwork. The pilot signal may be concurrently receivable by theplurality of cells within the network. In some embodiments, the pilotsignal may include a spatial signature (e.g., an SRS). In someembodiments, the pilot signal may be transmitted in a SIB requestoccasion indicated by system information request configurationinformation received with the synchronization signal, and may betransmitted with a random sequence usable by a base station totemporarily identify the UE during initial acquisition.

The system information processing module 705 may be used to receive, inresponse to transmitting the pilot signal, on-demand system informationfor the UE. The on-demand system information for the UE may include therandom sequence transmitted with the pilot signal, and in someembodiments may include an identifier of the UE.

The uplink/downlink allocation processing module 710 may be used toreceive, in response to transmitting the pilot signal, an uplinkallocation for the UE. The uplink/downlink allocation processing module710 may also be used to receiving a paging signal. By way of example,the paging signal may include a unicast paging signal or a multicastpaging signal.

The RRC connection management module 715 may be used to transmit an RRCconnection request to the network in response to receiving at least oneof on-demand system information for the UE or an uplink allocation forthe UE. In some embodiments, the network may allocate an active set ofresource or paging area for the UE upon the UE connecting to thenetwork, and may maintain an active context for the UE, in the network,until the UE leaves the network. In some embodiments, the UE 115-b mayenter a first RRC connected state upon initial access, and then switchbetween a plurality of RRC connected states (e.g., the first RRCconnected state and a second RRC connected state) based at least in parton a traffic level determined by the traffic level determination module750. The first RRC connected state may be associated with a first DRXcycle, and the second RRC connected state may be associated with asecond DRX cycle. The second DRX cycle may differ from the first DRXcycle, and in some embodiments, the second DRX cycle may be longer thanthe first DRX cycle.

When operating in the first RRC connected state, and according to thefirst DRX cycle, the scheduling request management module 720 maytransmit an SR, the buffer status report management module 725 maytransmit a BSR, the pilot signal transmission management module 645-amay transmit a connected state pilot signal (e.g., an SRS), or the CQImanagement module 730 may transmit an indicator of a channel qualitybased on a reference signal configured for and received by the UE 115-b.The connected state pilot signal may be transmitted using resources(e.g., time and frequency resources) identified by the network for theUE, and may include an identifier of the UE.

Also when operating in the first RRC connected state, theuplink/downlink allocation processing module 710 may monitor a grantchannel for an identifier of the UE. The grant channel may carry, forexample, paging signals or uplink grants for the UE 115-b.

Still further when operating in the first RRC connected state, themeasurement module 740 may measure a reference signal. In someembodiments, the reference signal may include a reference signalconfigured for and received by the UE 115-b (e.g., the reference signalon which the indicator of channel quality is based). In someembodiments, the reference signal may include a CSI-RS or beamformedCSI-RS received from the network. The constellation reselection module745 may be used to determine, based at least in part on a measurement ofthe keep alive signal or a decoding error of the keep alive signalperformed by the measurement module 740, whether to perform aconstellation reselection. When the constellation reselection module 745determines to perform a constellation reselection, the constellationreselection module 745 may perform the constellation reselection, andupon selecting the new constellation, the pilot signal transmissionmanagement module 645-a may transmit a pilot signal in response to asecond synchronization signal received from the new constellation.

When operating in the second RRC connected state, the pilot signaltransmission management module 645-a may be used to transmit a connectedstate pilot signal (e.g., an SRS) according to the second DRX cycle. Theconnected state pilot signal may be transmitted using resources (e.g.,time and frequency resources) identified by the network for the UE, andmay include an identifier of the UE. Also when operating in the secondRRC connected state, the UE may monitor a grant channel for anidentifier of the UE. The grant channel may carry, for example, a pagingsignal for the UE. Still further, and when operating in the second RRCconnected state, the UE may periodically measure a keep alive signalreceived from the network.

Also when operating in the second RRC connected state, the constellationreselection module 745 may be used to determine, based at least in parton a keep alive signal, whether to perform a constellation reselection.When the constellation reselection module 745 determines to perform aconstellation reselection, the constellation reselection module 745 mayperform the constellation reselection and, upon selecting the newconstellation, the pilot signal transmission management module 645-a maytransmit a pilot signal in response to a second synchronization signalreceived from the new constellation.

In some embodiments, the constellation reselection module 745 may beused to receive a reselection command from the network, and may select,in response to the reselection command, a new constellation.

The traffic level determination module 750 may be used to determine atraffic level (e.g., an uplink and/or downlink traffic level) for the UE115-b. In some embodiments, the traffic level may be determined based onat least one of: a network-transmitted traffic level indicator; anetwork command; a status of a timer maintained at the UE; or a bufferstatus of the UE. The traffic level determination module 750 may alsodetermine whether the traffic level satisfies a threshold. When thetraffic level satisfies the threshold, the RRC connection managementmodule 715 may switch the UE 115-b to (or maintain the UE 115-b in) thefirst RRC connected state. When the traffic level does not satisfy thethreshold, the RRC connection management module 715 may switch the UE115-b to (or maintain the UE 115-b in) the second RRC connected state.In some embodiments, the traffic level may be compared to a firstthreshold when determining whether to switch from the first RRCconnected state to the second RRC connected state, and the traffic levelmay be compared to a second threshold when determining whether to switchfrom the second RRC connected state to the first RRC connected state.

FIG. 8 shows a block diagram 800 of a base station 105-a for use inwireless communication, in accordance with various aspects of thepresent disclosure. The base station 105-a may be an example of aspectsof one or more of the base stations 105 described with reference toFIG. 1. The base station 105-a may also be or include a processor. Thebase station 105-a may include a receiver module 810, a wirelesscommunication management module 820, and a transmitter module 830. Eachof these modules may be in communication with each other.

The modules of the base station 105-a may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each module may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 810 may include at least one RFreceiver or at least one backhaul receiver. The backhaul receiver may beused for communicating with other base stations or a central node (e.g.,a node of a core network such as the core network 130 described withreference to FIG. 1). The receiver module 810, RF receiver, or backhaulreceiver may be used to receive various types of data or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links orbackhaul links of the wireless communication system 100 described withreference to FIG. 1.

In some examples, the transmitter module 830 may include at least one RFtransmitter or at least one backhaul transmitter. The transmitter module830, RF transmitter, or backhaul transmitter may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of a wireless communication system, such asone or more communication links or backhaul links of the wirelesscommunication system 100 described with reference to FIG. 1.

The wireless communication management module 820 may be used to manageone or more aspects of wireless communication for the base station105-a. In some examples, the wireless communication management module820 may include a synchronization signal broadcast module 835 or a pilotsignal reception management module 840.

The synchronization signal broadcast module 835 may be used to broadcasta synchronization signal. The synchronization signal may be common(e.g., non-cell specific) to a plurality of cells within a network, andmay be received from at least one of the plurality of cells (e.g., fromat least one of a plurality of base stations in the cells) as a SFNbroadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal may be aperiodic signal. In some embodiments, the synchronization signal mayinclude system information request (e.g., SIB request) configurationinformation. The configuration information may, in some examples,include at least one of an indication of a SIB request bandwidth, anindication of a SIB request timing (e.g., slot/symbol timing), a portionof a constellation identifier, or network access barring information(e.g., an indication of times when UEs of particular types may nottransmit a SIB request).

The pilot signal reception management module 840 may be used to receivea number of pilot signals from a first number of UEs. Each of the numberof pilot signals may identify a UE in the first number of UEs and beconcurrently receivable by the plurality of cells within the network.

FIG. 9 shows a block diagram 900 of a base station 105-b for use inwireless communication, in accordance with various aspects of thepresent disclosure. The base station 105-b may be an example of aspectsof one or more of the base stations 105 described with reference to FIG.1 or 8. The base station 105-b may also be or include a processor. Thebase station 105-b may include a receiver module 810, a wirelesscommunication management module 820-a, or a transmitter module 830. Eachof these modules may be in communication with each other.

The modules of the base station 105-b may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each module may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some embodiments, the receiver module 810 or transmitter module 830may be configured as described with reference to FIG. 8.

The wireless communication management module 820-a may be used to manageone or more aspects of wireless communication for the base station105-b. In some examples, the wireless communication management module820-a may include a synchronization signal broadcast module 835-a, apilot signal reception management module 845-a, or a serving cellmanagement module 905.

The synchronization signal broadcast module 835-a may be used tobroadcast a synchronization signal. The synchronization signal may becommon (e.g., non-cell specific) to a plurality of cells within anetwork, and may be received from at least one of the plurality of cells(e.g., from at least one of a plurality of base stations in the cells)as a SFN broadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal may be aperiodic signal. In some embodiments, the synchronization signal mayinclude system information request (e.g., SIB request) configurationinformation. The configuration information may, in some examples,include at least one of an indication of a SIB request bandwidth, anindication of a SIB request timing (e.g., slot/symbol timing), a portionof a constellation identifier, or network access barring information(e.g., an indication of times when UEs of particular types may nottransmit a SIB request).

The pilot signal reception management module 840-a may be used toreceive a number of pilot signals from a first number of UEs. Each ofthe number of pilot signals may identify a UE in the first number of UEsand be concurrently receivable by the plurality of cells within thenetwork.

The serving cell management module 905 may be used to identify, from thefirst number of UEs, a second number of UEs for which the base station105-b will serve as a serving cell. In some embodiments, the secondnumber of UEs may be identified locally at the base station 105-b, or ina distributed manner by the plurality of cells. In some embodiments, thesecond number of UEs may be identified by transmitting informationcorresponding to the number of pilot signals to a central node, andreceiving an indication of the second number of UEs from the centralnode.

The keep alive signal module 910 may be used when one or more of thesecond number of UEs is operating in the second RRC connected statedescribed with reference to FIG. 7, to transmit a keep alive signal tothe one or more of the second number of UEs. In some examples, differentkeep alive signals may be transmitted to different UEs.

In some embodiments of the method 2000 (discussed in more detail below),the base station may allocate an active set of resources or paging areato monitor the UE's mobility or traffic, and may alone, or incombination with other base stations or a central node, maintain anactive context for the UE until the UE leaves the network.

FIG. 10 shows a block diagram 1000 of a central node 1005 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the central node 1005 may be anode of the core network 130 described with reference to FIG. 1. Thecentral node 1005 may also be or include a processor. The central node1005 may include a receiver module 1010, a wireless communicationmanagement module 1020, or a transmitter module 1030. Each of thesemodules may be in communication with each other.

The modules of the central node 1005 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each module may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 1010 may include at least onebackhaul receiver. The backhaul receiver may be used for communicatingwith base stations, such as one or more of the base stations 105described with reference to FIG. 1, 8, or 9. The receiver module 1010 orbackhaul receiver may be used to receive various types of data orcontrol signals (i.e., transmissions) over one or more communicationlinks of a wireless communication system, such as one or morecommunication links or backhaul links of the wireless communicationsystem 100 described with reference to FIG. 1.

In some examples, the transmitter module 1030 may include at least onebackhaul transmitter. The backhaul transmitter may be used forcommunicating with base stations, such as one or more of the basestations 105 described with reference to FIG. 1, 8, or 9. Thetransmitter module 1030 or backhaul transmitter may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of a wireless communication system, such asone or more communication links or backhaul links of the wirelesscommunication system 100 described with reference to FIG. 1.

The wireless communication management module 1020 may be used to manageone or more aspects of wireless communication for one or more basestations in communication with the central node 1005 or one or more UEsin communication with the one or more base stations. In some examples,the wireless communication management module 1020 may include a pilotsignal information management module 1035 or a serving cellidentification module 1040.

The pilot signal information management module 1035 may be used toreceive, from each of a plurality of cells, information on a pilotsignal transmitted by a UE.

The serving cell identification module 1040 may be used to identify,from among the plurality of cells, and based at least in part on theinformation on the pilot signal received from one or more of theplurality of cells, a serving cell for the UE.

FIG. 11 shows a block diagram 1100 of a central node 1005-a for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the central node 1005-a may be anode of the core network 130 described with reference to FIG. 1. Thecentral node 1005-a may also be or include a processor. The central node1005-a may include a receiver module 1010, a wireless communicationmanagement module 1020-a, or a transmitter module 1030. Each of thesemodules may be in communication with each other.

The modules of the central node 1005-a may, individually orcollectively, be implemented using one or more ASICs adapted to performsome or all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on one or more integrated circuits. In other examples, othertypes of integrated circuits may be used (e.g., Structured/PlatformASICs, FPGAs, and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each module may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In some embodiments, the receiver module 1010 or transmitter module 1030may be configured as described with reference to FIG. 10.

The wireless communication management module 1020-a may be used tomanage one or more aspects of wireless communication for one or morebase stations in communication with the central node 1005-a or one ormore UEs in communication with the one or more base stations. In someexamples, the wireless communication management module 1020-a mayinclude a synchronization signal management module 1105, a pilot signalinformation management module 1035-a or a serving cell identificationmodule 1040-a.

The synchronization signal management module 1105 may be used toestablish a synchronization signal for transmission by a plurality ofcells in a network, to a number of UEs. The synchronization signal maybe common (e.g., non-cell specific) to the plurality of cells, and maybe received from at least one of the plurality of cells (e.g., from atleast one of a plurality of base stations in the cells) as a SFNbroadcast. The synchronization signal need not include a cellidentifier. In some examples, the synchronization signal may be aperiodic signal. In some embodiments, the synchronization signal mayinclude system information request (e.g., SIB request) configurationinformation. The configuration information may, in some examples,include at least one of an indication of a SIB request bandwidth, anindication of a SIB request timing (e.g., slot/symbol timing), a portionof a constellation identifier, or network access barring information(e.g., an indication of times when UEs of particular types may nottransmit a SIB request). In some embodiments, the synchronization signalmanagement module 1105 may provide an indication of the synchronizationsignal to each of the plurality of cells, and the synchronization signalmay be broadcast synchronously by the plurality of cells.

The pilot signal information management module 1035-a may be used toreceive, from each of the plurality of cells, information on a pilotsignal transmitted by a UE.

The serving cell identification module 1040-a may be used to identify,from among the plurality of cells, and based at least in part on theinformation on the pilot signal received from one or more of theplurality of cells, a serving cell for the UE.

FIG. 12 shows a block diagram 1200 of a UE 115-c for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. The UE 115-c may have various configurations and may beincluded or be part of a personal computer (e.g., a laptop computer, anetbook computer, a tablet computer, etc.), a cellular telephone, a PDA,a digital video recorder (DVR), an internet appliance, a gaming console,an e-reader, entertainment device, vehicular component, etc. The UE115-c may, in some examples, have an internal power supply (not shown),such as a small battery, to facilitate mobile operation. In someexamples, the UE 115-c may be an example of aspects of one or more ofthe UEs 115 described with reference to FIG. 1, 6, or 7. The UE 115-cmay be configured to implement at least some of the UE features andfunctions described with reference to FIG. 1, 2, 3, 4, 5, 6, or 7.

The UE 115-c may include a UE processor module 1210, a UE memory module1220, at least one UE transceiver module (represented by UE transceivermodule(s) 1230), at least one UE antenna (represented by UE antenna(s)1240), or a UE wireless communication management module 620-b. Each ofthese components may be in communication with each other, directly orindirectly, over one or more buses 1235.

The UE memory module 1220 may include random access memory (RAM) orread-only memory (ROM). The UE memory module 1220 may storecomputer-readable, computer-executable code 1225 containing instructionsthat are configured to, when executed, cause the UE processor module1210 to perform various functions described herein related to wirelesscommunication, including, for example, transmissions of a pilot signal.Alternatively, the code 1225 may not be directly executable by the UEprocessor module 1210 but be configured to cause the UE 115-c (e.g.,when compiled and executed) to perform various of the functionsdescribed herein.

The UE processor module 1210 may include an intelligent hardware device,e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc.The UE processor module 1210 may process information received throughthe UE transceiver module(s) 1230 or information to be sent to the UEtransceiver module(s) 1230 for transmission through the UE antenna(s)1240. The UE processor module 1210 may handle, alone or in connectionwith the UE wireless communication management module 620-b, variousaspects of communicating over (or managing communications over) awireless medium.

The UE transceiver module(s) 1230 may include a modem configured tomodulate packets and provide the modulated packets to the UE antenna(s)1240 for transmission, and to demodulate packets received from the UEantenna(s) 1240. The UE transceiver module(s) 1230 may, in someexamples, be implemented as one or more UE transmitter modules and oneor more separate UE receiver modules. The UE transceiver module(s) 1230may support communications on one or more wireless channels. The UEtransceiver module(s) 1230 may be configured to communicatebi-directionally, via the UE antenna(s) 1240, with one or more basestations, such as one or more of the base stations 105 described withreference to FIG. 1, 8, or 9. While the UE 115-c may include a single UEantenna, there may be examples in which the UE 115-c may includemultiple UE antennas 1240.

The UE state module 1250 may be used, for example, to manage transitionsof the UE 115-c between RRC connected states, and may be incommunication with other components of the UE 115-c, directly orindirectly, over the one or more buses 1235. The UE state module 1250,or portions of it, may include a processor, and/or some or all of thefunctions of the UE state module 1250 may be performed by the UEprocessor module 1210, in connection with the UE processor module 1210,or in connection with the UE wireless communication management module620-b.

The UE wireless communication management module 620-b may be configuredto perform or control some or all of the UE features or functionsdescribed with reference to FIG. 1, 2, 3, 4, 5, 6, or 7 related towireless communication. The UE wireless communication management module620-b, or portions of it, may include a processor, or some or all of thefunctions of the UE wireless communication management module 620-b maybe performed by the UE processor module 1210 or in connection with theUE processor module 1210. In some examples, the UE wirelesscommunication management module 620-b may be an example of the wirelesscommunication management module 620 described with reference to FIG. 6or 7.

FIG. 13 shows a block diagram 1300 of a base station 105-c (e.g., a basestation forming part or all of an eNB) for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the base station 105-c may be an exampleof one or more aspects of the base station 105 described with referenceto FIG. 1, 8, or 9. The base station 105-c may be configured toimplement or facilitate at least some of the base station features andfunctions described with reference to FIG. 1, 2, 3, 4, 5, 8, or 9.

The base station 105-c may include a base station processor module 1310,a base station memory module 1320, at least one base station transceivermodule (represented by base station transceiver module(s) 1350), atleast one base station antenna (represented by base station antenna(s)1355), or a base station wireless communication management module 820-b.The base station 105-c may also include one or more of a base stationcommunications module 1330 or a network communications module 1340. Eachof these components may be in communication with each other, directly orindirectly, over one or more buses 1335.

The base station memory module 1320 may include RAM or ROM. The basestation memory module 1320 may store computer-readable,computer-executable code 1325 containing instructions that areconfigured to, when executed, cause the base station processor module1310 to perform various functions described herein related to wirelesscommunication, including, for example, transmission of a synchronizationsignal. Alternatively, the code 1325 may not be directly executable bythe base station processor module 1310 but be configured to cause thebase station 105-g (e.g., when compiled and executed) to perform variousof the functions described herein.

The base station processor module 1310 may include an intelligenthardware device, e.g., a CPU, a microcontroller, an ASIC, etc. The basestation processor module 1310 may process information received throughthe base station transceiver module(s) 1350, the base stationcommunications module 1330, or the network communications module 1340.The base station processor module 1310 may also process information tobe sent to the transceiver module(s) 1350 for transmission through thebase station antenna(s) 1355, to the base station communications module1330, for transmission to one or more other base stations 105-d and105-e, or to the network communications module 1340 for transmission toa core network 130-a, which may be an example of one or more aspects ofthe core network 130 described with reference to FIG. 1. The basestation processor module 1310 may handle, alone or in connection withthe base station wireless communication management module 820-b, variousaspects of communicating over (or managing communications over) awireless medium.

The base station transceiver module(s) 1350 may include a modemconfigured to modulate packets and provide the modulated packets to thebase station antenna(s) 1355 for transmission, and to demodulate packetsreceived from the base station antenna(s) 1355. The base stationtransceiver module(s) 1350 may, in some examples, be implemented as oneor more base station transmitter modules and one or more separate basestation receiver modules. The base station transceiver module(s) 1350may support communications on one or more wireless channels. The basestation transceiver module(s) 1350 may be configured to communicatebi-directionally, via the base station antenna(s) 1355, with one or moreUEs, such as one or more of the UEs 115 described with reference to FIG.1, 6, 7, or 12. The base station 105-c may, for example, includemultiple base station antennas 1355 (e.g., an antenna array). The basestation 105-c may communicate with the core network 130-a through thenetwork communications module 1340. The base station 105-c may alsocommunicate with other base stations, such as the base stations 105-dand 105-e, using the base station communications module 1330.

The base station wireless communication management module 820-b may beconfigured to perform or control some or all of the base stationfeatures or functions described with reference to FIG. 1, 2, 3, 4, 5, 8,or 9 related to wireless communication. The base station wirelesscommunication management module 820-b, or portions of it, may include aprocessor, or some or all of the functions of the base station wirelesscommunication management module 820-b may be performed by the basestation processor module 1310 or in connection with the base stationprocessor module 1310. In some examples, the base station wirelesscommunication management module 820-b may be an example of the wirelesscommunication management module 820 described with reference to FIG. 8or 9.

FIG. 14 shows a block diagram 1400 of a central node 1005-b, inaccordance with various aspects of the present disclosure. In someexamples, the central node 1005-b may be an example of aspects of one ormore of the central nodes 1005 described with reference to FIG. 10 or11. In some examples, the central node 1005-b may be a node of the corenetwork 130 described with reference to FIG. 1. The central node 1005-bmay be configured to implement at least some of the central nodefeatures and functions described with reference to FIG. 2, 3, 4, 5, 10,or 11.

The central node 1005-b may include a central node processor module1410, a central node memory module 1420, a base station communicationsmodule 1430, or a central node wireless communication management module1020-b. Each of these components may be in communication with eachother, directly or indirectly, over one or more buses 1435.

The central node memory module 1420 may include RAM or ROM. The centralnode memory module 1420 may store computer-readable, computer-executablecode 1425 containing instructions that are configured to, when executed,cause the central node processor module 1410 to perform variousfunctions described herein related to wireless communication, including,for example, an identification of serving cells for each of a number ofUEs. Alternatively, the code 1425 may not be directly executable by thecentral node processor module 1410 but be configured to cause thecentral node 1005-b (e.g., when compiled and executed) to performvarious of the functions described herein.

The central node processor module 1410 may include an intelligenthardware device, e.g., a CPU, a microcontroller, an ASIC, etc. Thecentral node processor module 1410 may process information receivedthrough the base station communications module 1430 or information to besent to one or more base stations via the base station communicationsmodule 1430. The central node processor module 1410 may handle, alone orin connection with the central node wireless communication managementmodule 1020-b, various aspects of communicating over (or managingcommunications over) a wireless medium.

The base station communications module 1430 may be used by the centralnode 1005-b to communicate with one or more base stations 105-f and105-g. The base station communications module 1430 may be configured tocommunicate bi-directionally with the one or more base stations 105-fand 105-g. In some examples, the base stations 105-f and 105-g may beexamples of aspects of one or more of the base stations 105 describedwith reference to FIG. 1, 8, or 9.

The central node wireless communication management module 1020-b may beconfigured to perform or control some or all of the central nodefeatures or functions described with reference to FIG. 1, 2, 3, 4, 5,10, or 11 related to wireless communication between base stations andUEs. The central node wireless communication management module 1020-b,or portions of it, may include a processor, or some or all of thefunctions of the central node wireless communication management module1020-b may be performed by the central node processor module 1410 or inconnection with the central node processor module 1410. In someexamples, the central node wireless communication management module1020-b may be an example of the wireless communication management module1020 described with reference to FIG. 10 or 11.

FIG. 15 is a block diagram of a MIMO communication system 1500 includinga base station 105-h and a UE 115-d, in accordance with various aspectsof the present disclosure. The MIMO communication system 1500 mayillustrate aspects of the wireless communication system 100 describedwith reference to FIG. 1. The base station 105-h may be an example ofaspects of the base station 105 described with reference to FIG. 1, 8,9, or 13. The base station 105-h may be equipped with antennas 1534 and1535, and the UE 115-d may be equipped with antennas 1552 and 1553. Inthe MIMO communication system 1500, the base station 105-h may be ableto send data over multiple communication links at the same time. Eachcommunication link may be called a “layer” and the “rank” of thecommunication link may indicate the number of layers used forcommunication. For example, in a 2×2 MIMO communication system wherebase station 105-h transmits two “layers,” the rank of the communicationlink between the base station 105-h and the UE 115-d is two.

At the base station 105-h, a transmit (Tx) processor 1520 may receivedata from a data source. The transmit processor 1520 may process thedata. The transmit processor 1520 may also generate control symbols orreference symbols. A transmit MIMO processor 1530 may perform spatialprocessing (e.g., precoding) on data symbols, control symbols, orreference symbols, if applicable, and may provide output symbol streamsto the transmit modulator/demodulators 1532 and 1533. Eachmodulator/demodulator 1532 through 1533 may process a respective outputsymbol stream (e.g., for OFDM, etc.) to obtain an output sample stream.Each modulator/demodulator 1532 through 1533 may further process (e.g.,convert to analog, amplify, filter, and upconvert) the output samplestream to obtain a DL signal. In one example, DL signals frommodulator/demodulators 1532 and 1533 may be transmitted via the antennas1534 and 1535, respectively.

The UE 115-d may be an example of aspects of the UEs 115 described withreference to FIG. 1, 6, 7, or 12. At the UE 115-d, the UE antennas 1552and 1553 may receive the DL signals from the base station 105-h and mayprovide the received signals to the modulator/demodulators 1554 and1555, respectively. Each modulator/demodulator 1554 through 1555 maycondition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain input samples. Eachmodulator/demodulator 1554 through 1555 may further process the inputsamples (e.g., for OFDM, etc.) to obtain received symbols. A MIMOdetector 1556 may obtain received symbols from themodulator/demodulators 1554 and 1555, perform MIMO detection on thereceived symbols, if applicable, and provide detected symbols. A receive(Rx) processor 1558 may process (e.g., demodulate, deinterleave, anddecode) the detected symbols, providing decoded data for the UE 115-d toa data output, and provide decoded control information to a processor1580, or memory 1582.

The processor 1580 may in some cases execute stored instructions toinstantiate a UE wireless communication management module 620-c. The UEwireless communication management module 620-c may be an example ofaspects of the wireless communication management module 620 describedwith reference to FIG. 6, 7, or 12.

On the uplink (UL), at the UE 115-d, a transmit processor 1564 mayreceive and process data from a data source. The transmit processor 1564may also generate reference symbols for a reference signal. The symbolsfrom the transmit processor 1564 may be precoded by a transmit MIMOprocessor 1566 if applicable, further processed by themodulator/demodulators 1554 and 1555 (e.g., for SC-FDMA, etc.), and betransmitted to the base station 105-h in accordance with thecommunication parameters received from the base station 105-h. At thebase station 105-h, the UL signals from the UE 115-d may be received bythe antennas 1534 and 1535, processed by the modulator/demodulators 1532and 1533, detected by a MIMO detector 1536 if applicable, and furtherprocessed by a receive processor 1538. The receive processor 1538 mayprovide decoded data to a data output and to the processor 1540 ormemory 1542.

The processor 1540 may in some cases execute stored instructions toinstantiate a base station wireless communication management module820-c. The base station wireless communication management module 820-cmay be an example of aspects of the wireless communication managementmodule 820 described with reference to FIG. 8, 9, or 13.

The components of the UE 115-d may, individually or collectively, beimplemented with one or more ASICs adapted to perform some or all of theapplicable functions in hardware. Each of the noted modules may be ameans for performing one or more functions related to operation of theMIMO communication system 1500. Similarly, the components of the basestation 105-h may, individually or collectively, be implemented with oneor more ASICs adapted to perform some or all of the applicable functionsin hardware. Each of the noted components may be a means for performingone or more functions related to operation of the MIMO communicationsystem 1500.

FIG. 16 is a flow chart illustrating an example of a method 1600 forwireless communication at a UE, in accordance with various aspects ofthe present disclosure. For clarity, the method 1600 is described belowwith reference to aspects of one or more of the UEs 115 described withreference to FIG. 1, 6, 7, 12, or 15. In some examples a UE may executeone or more sets of codes to control the functional elements of the UEto perform the functions described below. In some examples, the method1600 may be performed by a UE during an initial access procedure.

At block 1605, a UE may receive a synchronization signal. Thesynchronization signal may be common (e.g., non-cell specific) to aplurality of cells within a network, and may be received from at leastone of the plurality of cells (e.g., from at least one of a plurality ofbase stations in the cells) as a SFN broadcast. The synchronizationsignal need not include a cell identifier. In some examples, thesynchronization signal may be a periodic signal. In some embodiments,the synchronization signal may include system information request (e.g.,SIB request) configuration information. The configuration informationmay, in some examples, include at least one of an indication of a SIBrequest bandwidth, an indication of a SIB request timing (e.g.,slot/symbol timing), a portion of a constellation identifier, or networkaccess barring information (e.g., an indication of times when UEs ofparticular types may not transmit a SIB request). The operation(s) atblock 1605 may be performed using the wireless communication managementmodule 620 described with reference to FIG. 6, 7, 12, or 15, or thesynchronization signal processing module 635 described with reference toFIG. 6 or 7.

At block 1610, the UE may acquire a timing of the network based on thesynchronization signal. The operation(s) at block 1610 may be performedusing the wireless communication management module 620 described withreference to FIG. 6, 7, 12, or 15, or the network timing acquisitionmodule 640 described with reference to FIG. 6 or 7.

At block 1615, the UE may transmit a pilot signal in response toacquiring the timing of the network. The pilot signal may beconcurrently receivable by the plurality of cells within the network. Insome embodiments, the pilot signal may include a spatial signature(e.g., an SRS). In some embodiments, the pilot signal may be transmittedin a SIB request occasion indicated by system information requestconfiguration information received with the synchronization signal, andmay be transmitted with a random sequence usable by a base station totemporarily identify the UE during initial acquisition. The operation(s)at block 1615 may be performed using the wireless communicationmanagement module 620 described with reference to FIG. 6, 7, 12, or 15,or the pilot signal transmission management module 645 described withreference to FIG. 6 or 7. Further examples of the synchronization signalor pilot signal are described with reference to FIG. 2.

Thus, the method 1600 may provide for wireless communication. It shouldbe noted that the method 1600 is just one implementation and that theoperations of the method 1600 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 17 is a flow chart illustrating an example of a method 1700 forwireless communication at a UE, in accordance with various aspects ofthe present disclosure. For clarity, the method 1700 is described belowwith reference to aspects of one or more of the UEs 115 described withreference to FIG. 1, 6, 7, 12, or 15. In some examples a UE may executeone or more sets of codes to control the functional elements of the UEto perform the functions described below. In some examples, the method1700 may be performed by a UE during an initial access procedure.

At block 1705, a UE may receive a synchronization signal. Thesynchronization signal may be common (e.g., non-cell specific) to aplurality of cells within a network, and may be received from at leastone of the plurality of cells (e.g., from at least one of a plurality ofbase stations in the cells) as a SFN broadcast. The synchronizationsignal need not include a cell identifier. In some examples, thesynchronization signal may be a periodic signal. In some embodiments,the synchronization signal may include system information request (e.g.,SIB request) configuration information. The configuration informationmay, in some examples, include at least one of an indication of a SIBrequest bandwidth, an indication of a SIB request timing (e.g.,slot/symbol timing), a portion of a constellation identifier, or networkaccess barring information (e.g., an indication of times when UEs ofparticular types may not transmit a SIB request). The operation(s) atblock 1705 may be performed using the wireless communication managementmodule 620 described with reference to FIG. 6, 7, 12, or 15, or thesynchronization signal processing module 635 described with reference toFIG. 6 or 7.

At block 1710, the UE may acquire a timing of the network based on thesynchronization signal. The operation(s) at block 1710 may be performedusing the wireless communication management module 620 described withreference to FIG. 6, 7, 12, or 15, or the network timing acquisitionmodule 640 described with reference to FIG. 6 or 7.

At block 1715, the UE may transmit a pilot signal in response toacquiring the timing of the network. The pilot signal may beconcurrently receivable by the plurality of cells within the network. Insome embodiments, the pilot signal may include a spatial signature(e.g., an SRS). In some embodiments, the pilot signal may be transmittedin a SIB request occasion indicated by system information requestconfiguration information received with the synchronization signal, andmay be transmitted with a random sequence usable by a base station totemporarily identify the UE during initial acquisition. The operation(s)at block 1715 may be performed using the wireless communicationmanagement module 620 described with reference to FIG. 6, 7, 12, or 15,or the pilot signal transmission management module 645 described withreference to FIG. 6 or 7. Further examples of the synchronization signalor pilot signal are described with reference to FIG. 2.

At block 1720, the UE may receive, in response to transmitting the pilotsignal, at least one of on-demand system information for the UE anuplink allocation for the UE, or a downlink control channel message. Theon-demand system information for the UE or the uplink allocation for theUE may include the random sequence transmitted with the pilot signal,and in some embodiments may include an identifier of the UE. Theoperation(s) at block 1720 may be performed using the wirelesscommunication management module 620 described with reference to FIG. 6,7, 12, or 15, or the system information processing module 705 oruplink/downlink allocation processing module 710 described withreference to FIG. 7.

At block 1725, the UE may transmit an RRC connection request to thenetwork in response to receiving at least one of the on-demand systeminformation for the UE or the uplink allocation for the UE. Theoperation(s) at block 1725 may be performed using the wirelesscommunication management module 620 described with reference to FIG. 6,7, 12, or 15, or the RRC connection management module 715 described withreference to FIG. 7.

Thus, the method 1700 may provide for wireless communication. It shouldbe noted that the method 1700 is just one implementation and that theoperations of the method 1700 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 18 is a flow chart illustrating an example of a method 1800 forwireless communication at a UE, in accordance with various aspects ofthe present disclosure. For clarity, the method 1800 is described belowwith reference to aspects of one or more of the UEs 115 described withreference to FIG. 1, 6, 7, 12, or 15. In some examples a UE may executeone or more sets of codes to control the functional elements of the UEto perform the functions described below. in some embodiments, themethod 1800 may begin with a UE commencing entry into an RRC connectedstate (e.g., a first RRC connected state), as described with referenceto block 1725 of FIG. 17. The UE may then switch between a plurality ofRRC connected states, including the first RRC connected state, based atleast in part on a determined traffic level (e.g., a traffic levelbetween the UE and the network).

At block 1805, the UE may enter or remain in a first RRC connected statewith a network. In some embodiments, the first RRC connected state maybe associated with a first DRX cycle. The operation(s) at block 1805 maybe performed using the wireless communication management module 620described with reference to FIG. 6, 7, 12, or 15, or the RRC connectionmanagement module 715 described with reference to FIG. 7.

At block 1810, and when operating in the first RRC connected state, theUE may transmit, according to the first DRX cycle, at least one of: anSR, a BSR, a connected state pilot signal (e.g., an SRS), or anindicator of a channel quality based on a reference signal configuredfor and received by the UE. The connected state pilot signal may betransmitted using resources (e.g., time and frequency resources)identified by the network for the UE, and may include an identifier ofthe UE. The operation(s) at block 1810 may be performed using thewireless communication management module 620 described with reference toFIG. 6, 7, 12, or 15, the pilot signal transmission management module645 described with reference to FIG. 6 or 7, or the scheduling requestmanagement module 720, buffer status report management module 725, orCQI management module 730 described with reference to FIG. 7.

At block 1815, and when operating in the first RRC connected state, theUE may monitor a grant channel for the identifier of the UE. The grantchannel may carry, for example, paging signals or uplink grants for theUE. The operation(s) at block 1815 may be performed using the wirelesscommunication management module 620 described with reference to FIG. 6,7, 12, or 15, or the grant management module 735 described withreference to FIG. 7.

At block 1820, and when operating in the first RRC connected state, theUE may measure a reference signal. In some embodiments, the referencesignal may include a reference signal configured for and received by theUE (e.g., the reference signal on which the indicator of the channelquality, transmitted at block 1910, is based). In some embodiments, thereference signal may include a CSI-RS or beamformed CSI-RS received fromthe network. The operation(s) at block 1820 may be performed using thewireless communication management module 620 described with reference toFIG. 6, 7, 12, or 15, or the measurement module 740 described withreference to FIG. 7.

At block 1825, and when operating in the first RRC connected state, theUE may determine, based at least in part on the measurement of thereference signal at block 1820, whether to perform a constellationreselection. When a determination is made to perform a constellationreselection, the method 1800 may continue at block 1830. When adetermination is made to not perform a constellation reselection, themethod 1800 may continue at block 1835. The operation(s) at block 1825may be performed using the wireless communication management module 620described with reference to FIG. 6, 7, 12, or 15, or the constellationreselection module 745 described with reference to FIG. 7.

At block 1830, the UE may perform a constellation reselection based atleast in part on a measurement of the keep alive signal or a decodingerror of the keep alive signal performed at block 1820. Upon selecting anew constellation, the UE may transmit a pilot signal in response to asecond synchronization signal received from the new constellation. Theoperation(s) at block 1830 may be performed using the wirelesscommunication management module 620 described with reference to FIG. 6,7, 12, or 15, or the constellation reselection module 745 described withreference to FIG. 7.

At block 1835, the UE may determine a traffic level. In someembodiments, the traffic level may be determined based on at least oneof: a network-transmitted traffic level indicator; a network command; astatus of a timer maintained at the UE; or a buffer status of the UE. Atblock 1840, it may be determined whether the traffic level satisfies athreshold. When it is determined that the traffic level satisfies thethreshold, the method 1800 may continue at block 1805. When it isdetermined that the traffic level does not satisfy the threshold, themethod 1800 may continue at block 1845. In some embodiments, the trafficlevel may be compared to a first threshold when determining whether toswitch from the first RRC connected state to the second RRC connectedstate, and the traffic level may be compared to a second threshold whendetermining whether to switch from the second RRC connected state to thefirst RRC connected state. The operation(s) at block 1835 or 1840 may beperformed using the wireless communication management module 620described with reference to FIG. 6, 7, 12, or 15, or the traffic leveldetermination module 750 described with reference to FIG. 7.

At block 1845, the UE may enter or remain in a second RRC connectedstate with the network. In some embodiments, the second RRC connectedstate may be associated with a second DRX cycle. The second DRX cyclemay differ from the first DRX cycle, and in some embodiments, the secondDRX cycle may be longer than the first DRX cycle. The operation(s) atblock 1845 may be performed using the wireless communication managementmodule 620 described with reference to FIG. 6, 7, 12, or 15, or the RRCconnection management module 715 described with reference to FIG. 7.

At block 1850, and when operating in the second RRC connected state, theUE may transmit a connected state pilot signal (e.g., an SRS) accordingto the second DRX cycle. The connected state pilot signal transmittedmay be transmitted using resources (e.g., time and frequency resources)identified by the network for the UE, and may include an identifier ofthe UE. The operation(s) at block 1850 may be performed using thewireless communication management module 620 described with reference toFIG. 6, 7, 12, or 15, or the pilot signal transmission management module645 described with reference to FIG. 6 or 7.

At block 1855, and when operating in the second RRC connected state, theUE may monitor a grant channel for the identifier of the UE. The grantchannel may carry, for example, a paging signal for the UE. Theoperation(s) at block 1855 may be performed using the wirelesscommunication management module 620 described with reference to FIG. 6,7, 12, or 15, or the grant management module 735 described withreference to FIG. 7.

At block 1860, and when operating in the second RRC connected state, theUE may measure a keep alive signal received from the network. The UE maydetermine, based at least in part on a measurement of the keep alivesignal, whether to perform a constellation reselection (e.g., at block1825). The operation(s) at block 1860 may be performed using thewireless communication management module 620 described with reference toFIG. 6, 7, 12, or 15, or the measurement module 740 described withreference to FIG. 7.

In some embodiments of the method 1800, and in addition or alternativelyto any constellation reselection performed at block 1830, the method1800 may include receiving a reselection command from the network, andselecting, in response to the reselection command, a new constellation.

Thus, the method 1800 may provide for wireless communication. It shouldbe noted that the method 1800 is just one implementation and that theoperations of the method 1800 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 19 is a flow chart illustrating an example of a method 1900 forwireless communication at a base station, in accordance with variousaspects of the present disclosure. For clarity, the method 1900 isdescribed below with reference to aspects of one or more of the basestations 105 described with reference to FIG. 1, 8, 9, 13, or 15. Insome examples a base station may execute one or more sets of codes tocontrol the functional elements of the base station to perform thefunctions described below.

At block 1905, a base station may broadcast a synchronization signal.The synchronization signal may be common (e.g., non-cell specific) to aplurality of cells within a network, and may be received from at leastone of the plurality of cells (e.g., from at least one of a plurality ofbase stations in the cells) as a SFN broadcast. The synchronizationsignal need not include a cell identifier. In some examples, thesynchronization signal may be a periodic signal. In some embodiments,the synchronization signal may include system information request (e.g.,SIB request) configuration information. The configuration informationmay, in some examples, include at least one of an indication of a SIBrequest bandwidth, an indication of a SIB request timing (e.g.,slot/symbol timing), a portion of a constellation identifier, or networkaccess barring information (e.g., an indication of times when UEs ofparticular types may not transmit a SIB request). The operation(s) atblock 1905 may be performed using the wireless communication managementmodule 820 described with reference to FIG. 8, 9, 13, or 15, or thesynchronization signal broadcast module 835 described with reference toFIG. 8 or 9.

At block 1910, the base station may receive a number of pilot signalsfrom a first number of UEs. Each of the number of pilot signals mayidentify a UE in the first number of UEs and be concurrently receivableby the plurality of cells within the network. The operation(s) at block1910 may be performed using the wireless communication management module820 described with reference to FIG. 8, 9, 13, or 15, or the pilotsignal reception management module 840 described with reference to FIG.8 or 9.

Thus, the method 1900 may provide for wireless communication. It shouldbe noted that the method 1900 is just one implementation and that theoperations of the method 1900 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 20 is a flow chart illustrating an example of a method 2000 forwireless communication at a base station, in accordance with variousaspects of the present disclosure. For clarity, the method 2000 isdescribed below with reference to aspects of one or more of the basestations 105 described with reference to FIG. 1, 8, 9, 13, or 15. Insome examples a base station may execute one or more sets of codes tocontrol the functional elements of the base station to perform thefunctions described below.

At block 2005, a base station may broadcast a synchronization signal.The synchronization signal may be common (e.g., non-cell specific) to aplurality of cells within a network, and may be received from at leastone of the plurality of cells (e.g., from at least one of a plurality ofbase stations in the cells) as a SFN broadcast. The synchronizationsignal need not include a cell identifier. In some examples, thesynchronization signal may be a periodic signal. In some embodiments,the synchronization signal may include system information request (e.g.,SIB request) configuration information. The configuration informationmay, in some examples, include at least one of an indication of a SIBrequest bandwidth, an indication of a SIB request timing (e.g.,slot/symbol timing), a portion of a constellation identifier, or networkaccess barring information (e.g., an indication of times when UEs ofparticular types may not transmit a SIB request). The operation(s) atblock 2005 may be performed using the wireless communication managementmodule 820 described with reference to FIG. 8, 9, 13, or 15, or thesynchronization signal broadcast module 835 described with reference toFIG. 8 or 9.

At block 2010, the base station may receive a number of pilot signalsfrom a first number of UEs. Each of the number of pilot signals mayidentify a UE in the first number of UEs and be concurrently receivableby the plurality of cells within the network. The operation(s) at block2010 may be performed using the wireless communication management module820 described with reference to FIG. 8, 9, 13, or 15, or the pilotsignal reception management module 840 described with reference to FIG.8 or 9.

At block 2015, the base station may identify, from the first number ofUEs, a second number of UEs for which the base station will serve as aserving cell. In some embodiments, the second number of UEs may beidentified locally at the base station, or in a distributed manner bythe plurality of cells. In some embodiments, the second number of UEsmay be identified by transmitting information corresponding to thenumber of pilot signals to a central node, and receiving an indicationof the second number of UEs from the central node. The operation(s) atblock 2015 may be performed using the wireless communication managementmodule 820 described with reference to FIG. 8, 9, 13, or 15, or theserving cell management module 905 described with reference to FIG. 9.

At block 2020, and when one or more of the second number of UEs isoperating in the second RRC connected state described with reference toFIG. 18, the base station may transmit a keep alive signal to the one ormore of the second number of UEs. In some examples, different keep alivesignals may be transmitted to different UEs. The operation(s) at block2020 may be performed using the wireless communication management module820 described with reference to FIG. 8, 9, 13, or 15, or the keep alivesignal module 910 described with reference to FIG. 9.

In some embodiments of the method 2000, the base station may allocate anactive set of resources or paging area to monitor the UE's mobility ortraffic, and may alone, or in combination with other base stations or acentral node, maintain an active context for the UE until the UE leavesthe network.

Thus, the method 2000 may provide for wireless communication. It shouldbe noted that the method 2000 is just one implementation and that theoperations of the method 2000 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 21 is a flow chart illustrating an example of a method 2100 formanaging wireless communication at a central node, in accordance withvarious aspects of the present disclosure. For clarity, the method 2100is described below with reference to aspects of one or more of thecentral nodes 1005 described with reference to FIG. 10, 11, or 14. Insome examples a central node may execute one or more sets of codes tocontrol the functional elements of the central node to perform thefunctions described below.

At block 2105, a central node may receive, from each of a plurality ofcells, information on a pilot signal transmitted by a UE. Theoperation(s) at block 2105 may be performed using the wirelesscommunication management module 1020 described with reference to FIG.10, 11, or 14, or the pilot signal information management module 1035described with reference to FIG. 10 or 11.

At block 2110, the central node may identify, from among the pluralityof cells, and based at least in part on the information on the pilotsignal received from one or more of the plurality of cells, a servingcell for the UE. The operation(s) at block 2110 may be performed usingthe wireless communication management module 1020 described withreference to FIG. 10, 11, or 14, or the serving cell identificationmodule 1040 described with reference to FIG. 10 or 11.

Thus, the method 2100 may provide for wireless communication. It shouldbe noted that the method 2100 is just one implementation and that theoperations of the method 2100 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 22 is a flow chart illustrating an example of a method 2200 formanaging wireless communication at a central node, in accordance withvarious aspects of the present disclosure. For clarity, the method 2200is described below with reference to aspects of one or more of thecentral nodes 1005 described with reference to FIG. 10, 11, or 14. Insome examples a central node may execute one or more sets of codes tocontrol the functional elements of the central node to perform thefunctions described below.

At block 2205, a central node may establish a synchronization signal fortransmission by a plurality of cells in a network, to a number of UEs.The synchronization signal may be common (e.g., non-cell specific) tothe plurality of cells. and may be received from at least one of theplurality of cells (e.g., from at least one of a plurality of basestations in the cells) as a SFN broadcast. The synchronization signalneed not include a cell identifier. In some examples, thesynchronization signal may be a periodic signal. In some embodiments,the synchronization signal may include system information request (e.g.,SIB request) configuration information. The configuration informationmay, in some examples, include at least one of an indication of a SIBrequest bandwidth, an indication of a SIB request timing (e.g.,slot/symbol timing), a portion of a constellation identifier, or networkaccess barring information (e.g., an indication of times when UEs ofparticular types may not transmit a SIB request). The operation(s) atblock 2205 may be performed using the wireless communication managementmodule 1020 described with reference to FIG. 10, 11, or 14, or thesynchronization signal management module 1105 described with referenceto FIG. 11.

At block 2210, the central node may receive, from each of the pluralityof cells, information on a pilot signal transmitted by a UE. Theoperation(s) at block 2210 may be performed using the wirelesscommunication management module 1020 described with reference to FIG.10, 11, or 14, or the pilot signal information management module 1035described with reference to FIG. 10 or 11.

At block 2215, the central node may identify, from among the pluralityof cells, and based at least in part on the information on the pilotsignal received from one or more of the plurality of cells, a servingcell for the UE. The operation(s) at block 2215 may be performed usingthe wireless communication management module 1020 described withreference to FIG. 10, 11, or 14, or the serving cell identificationmodule 1040 described with reference to FIG. 10 or 11.

Thus, the method 2200 may provide for wireless communication. It shouldbe noted that the method 2200 is just one implementation and that theoperations of the method 2200 may be rearranged or otherwise modifiedsuch that other implementations are possible.

The detailed description set forth above in connection with the appendeddrawings describes examples and does not represent the only examplesthat may be implemented or that are within the scope of the claims. Theterms “example” and “exemplary,” when used in this description, mean“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand apparatuses are shown in block diagram form in order to avoidobscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on anon-transitory computer-readable medium. Other examples andimplementations are within the scope and spirit of the disclosure andappended claims. For example, due to the nature of software, functionsdescribed above can be implemented using software executed by aprocessor, hardware, firmware, hardwiring, or combinations of any ofthese. Features implementing functions may also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations. Also, as usedherein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of” indicates a disjunctive list such that,for example, a list of “at least one of A, B, or C” means A or B or C orAB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the common principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication at a userequipment (UE), comprising: transmitting a pilot signal to a pluralityof base stations of a wireless network; receiving from the wirelessnetwork, in response to transmitting the pilot signal, a keep alivesignal from a previously non-serving base station of the plurality ofbase stations; and undergoing, based at least in part on the pilotsignal, a handover of the UE from a previously serving base station ofthe plurality of base stations to the previously non-serving basestation of the plurality of base stations.
 2. The method of claim 1,wherein transmitting a pilot signal comprises transmitting a firstinstance of the pilot signal and transmitting a second instance of thepilot signal, and wherein receiving a keep alive signal comprisesreceiving a first keep alive signal from the previously serving basestation based at least in part on transmitting the first instance of thepilot signal, and receiving a second keep alive signal from thepreviously non-serving base station based at least in part ontransmitting the second instance of the pilot signal.
 3. The method ofclaim 2, wherein the UE transmits the first instance of the pilot signaland the second instance of the pilot signal from different locationswithin the wireless network.
 4. The method of claim 1, wherein the pilotsignal is transmitted using resources allocated for the UE.
 5. Themethod of claim 1, wherein the pilot signal comprises at least one of: aspatial signature, a sounding reference signal (SRS), a pre-determinedrandom sequence, a random sequence generated by the UE, or a sequencehashed from a unique identifier of the UE.
 6. A device for wirelesscommunication at a user equipment (UE), comprising a processor, memoryin electronic communication with the processor, and instructions storedin the memory, the instructions being executable by the processor to:transmit a pilot signal to a plurality of base stations of a wirelessnetwork; receive from the wireless network, in response to transmittingthe pilot signal, a keep alive signal from a previously non-serving basestation of the plurality of base stations; and undergoing a handover ofthe UE from a previously serving base station of the plurality of basestations to the previously non-serving base station of the plurality ofbase stations based at least in part on the pilot signal.
 7. The deviceof claim 6, wherein: the instructions executable by the processor totransmit the pilot signal comprise instructions to transmit a firstinstance of the pilot signal and transmit a second instance of the pilotsignal, and the instructions executable by the processor to receive akeep alive signal comprise instructions to receive a first keep alivesignal from the previously serving base station based at least in parton transmitting the first instance of the pilot signal, and receive asecond keep alive signal from the previously non-serving base stationbased at least in part on transmitting the second instance of the pilotsignal.
 8. The device of claim 7, wherein the UE transmits the firstinstance of the pilot signal and the second instance of the pilot signalfrom different locations within the wireless network.
 9. The device ofclaim 6, wherein the pilot signal is transmitted using resourcesallocated for the UE.
 10. The device of claim 6, wherein the pilotsignal comprises at least one of: a spatial signature, a soundingreference signal (SRS), a pre-determined random sequence, a randomsequence generated by the UE, or a sequence hashed from a uniqueidentifier of the UE.
 11. A device for wireless communication at a userequipment (UE), comprising: means for transmitting a pilot signal to aplurality of base stations of a wireless network; means for receivingfrom the wireless network, in response to transmitting the pilot signal,a keep alive signal from a previously non-serving base station of theplurality of base stations; and means for undergoing a handover of theUE from a previously serving cell of the plurality of base stations tothe previously non-serving second serving cell of the plurality of basestations based at least in part on the pilot signal.
 12. The device of11, wherein the means for transmitting a pilot signal comprises meansfor transmitting a first instance of the pilot signal and means fortransmitting a second instance of the pilot signal, and wherein themeans for receiving a keep alive signal comprises means for receiving afirst keep alive signal from the previously serving base station basedat least in part on transmitting the first instance of the pilot signal,and means for receiving a second keep alive signal from the previouslynon-serving base station based at least in part on transmitting thesecond instance of the pilot signal.
 13. The device of claim 12, whereinthe UE transmits the first instance of the pilot signal and the secondinstance of the pilot signal from different locations within thewireless network.
 14. The device of claim 11, wherein the pilot signalis transmitted using resources allocated for the UE.
 15. The device ofclaim 11, wherein the pilot signal comprises at least one of: a spatialsignature, a sounding reference signal (SRS), a pre-determined randomsequence, a random sequence generated by the UE, or a sequence hashedfrom a unique identifier of the UE.
 16. A non-transitorycomputer-readable medium storing computer-executable code for wirelesscommunication at a user equipment (UE), the code executable by aprocessor to: transmit a pilot signal to a plurality of base stations ofa wireless network; receive from the wireless network, in response totransmitting the pilot signal, a keep alive signal from a previouslynon-serving base station of the plurality of base stations; and undergoa handover of the UE from a previously serving cell of the plurality ofbase stations to the previously non-serving cell of the plurality ofbase stations based at least in part on the pilot signal.
 17. Thenon-transitory computer-readable medium of claim 16, wherein: the codeexecutable by the processor to transmit a pilot signal comprises codeexecutable by the processor to transmit a first instance of the pilotsignal and transmit a second instance of the pilot signal; and the codeexecutable by the processor to receive a keep alive signal comprisescode executable by the processor to receive a first keep alive signalfrom the previously serving base station based at least in part ontransmitting the first instance of the pilot signal, and receive asecond keep alive signal from the previously non-serving base stationbased at least in part on transmitting the second instance of the pilotsignal.
 18. The non-transitory computer-readable medium of claim 17,wherein the UE transmits the first instance of the pilot signal and thesecond instance of the pilot signal from different locations within thewireless network.
 19. The non-transitory computer-readable medium ofclaim 16, wherein the pilot signal is transmitted using resourcesallocated for the UE.
 20. The non-transitory computer-readable medium ofclaim 16, wherein the pilot signal comprises at least one of: a spatialsignature, a sounding reference signal (SRS), a pre-determined randomsequence, a random sequence generated by the UE, or a sequence hashedfrom a unique identifier of the UE.